Prescription
Fertilizers for Trees and Shrubs
Fertilizers for Trees and Shrubs
Notes to the
PowerPoint Presentation
PowerPoint Presentation
Desert Green 2013
Robert Ll. Morris, Emeritus
University of Nevada
Desert Green is a conference held annually in Las Vegas for landscape professionals. This is a copy of my presentation on PowerPoint and my notes for the presentation.
Slide 1. Title slide with contact information.
Slide 2. Characteristics
of desert soils. Desert soils contain very little organic matter and they
are chemically and physically undeveloped. Because they contain so little
organic matter in them, they have very little structure or are structureless.
For this reason they sometimes tend to drain poorly. Their alkalinity or pH is
normally high. Frequently they contain high levels of salt of all different
types. If these soils have never been developed, they can change rapidly both
physically and chemically when water is applied to them.
of desert soils. Desert soils contain very little organic matter and they
are chemically and physically undeveloped. Because they contain so little
organic matter in them, they have very little structure or are structureless.
For this reason they sometimes tend to drain poorly. Their alkalinity or pH is
normally high. Frequently they contain high levels of salt of all different
types. If these soils have never been developed, they can change rapidly both
physically and chemically when water is applied to them.
Slide 3. There are 16 or 17 nutrients that are essential
to plants. Several of these are needed in large amounts and we call these major
elements or macronutrients. The rest of the nutrients are needed in a much
smaller amounts, still just as essential. These are referred to as minor or
micronutrients. All of these nutrients are essential to plant life and if any
one of them is missing, the plant will die. If any of these are insufficient
for the plant, it can display visual symptoms, poor health and subject to
increased disease and insect problems. Bags of fertilizer traditionally contain
nitrogen, phosphorus and potassium if they are a complete fertilizer. These
three nutrients are called NPK and their relative amounts determine the fertilizer
ratio. Carbon, hydrogen and oxygen the plant obtains from air and water. Most
desert soils contain adequate amounts of calcium, magnesium and sulfur. Of the
minor elements, iron, manganese and zinc can be in short supply to plants
because of the soil’s alkalinity or high pH. In most desert soils were
landscape plants are being grown, nitrogen is most commonly found in the
greatest need by plants. Second to nitrogen is probably available iron.
to plants. Several of these are needed in large amounts and we call these major
elements or macronutrients. The rest of the nutrients are needed in a much
smaller amounts, still just as essential. These are referred to as minor or
micronutrients. All of these nutrients are essential to plant life and if any
one of them is missing, the plant will die. If any of these are insufficient
for the plant, it can display visual symptoms, poor health and subject to
increased disease and insect problems. Bags of fertilizer traditionally contain
nitrogen, phosphorus and potassium if they are a complete fertilizer. These
three nutrients are called NPK and their relative amounts determine the fertilizer
ratio. Carbon, hydrogen and oxygen the plant obtains from air and water. Most
desert soils contain adequate amounts of calcium, magnesium and sulfur. Of the
minor elements, iron, manganese and zinc can be in short supply to plants
because of the soil’s alkalinity or high pH. In most desert soils were
landscape plants are being grown, nitrogen is most commonly found in the
greatest need by plants. Second to nitrogen is probably available iron.
Slide 4. The three numbers on the fertilizer bag give an
indicator of the amount of nitrogen, phosphorus and potassium contained in the
bag, in that order. Sometimes there is a fourth number present. Although not
legally required it usually represents the amount of sulfur contained in the
fertilizer. The fertilizer ratio tells us the relative amounts of NPK. For
instance, if the fertilizer has a ratio of NPK of 3:1:2 then fertilizers such
as 12-4-8 and 21-7-14 would represent this ratio.
indicator of the amount of nitrogen, phosphorus and potassium contained in the
bag, in that order. Sometimes there is a fourth number present. Although not
legally required it usually represents the amount of sulfur contained in the
fertilizer. The fertilizer ratio tells us the relative amounts of NPK. For
instance, if the fertilizer has a ratio of NPK of 3:1:2 then fertilizers such
as 12-4-8 and 21-7-14 would represent this ratio.
Slide 5. Although all nutrients are needed for a plant to
live, nitrogen represents the one nutrient that is universally in short supply.
Nitrogen helps to drive plant growth and causes increases in size. It
stimulates increased leaf and stem growth, causes a darkening of leaf color,
hastens plant growth after winter dormancy and helps to increase the amount of
food manufactured by the plant. If applied too late in the year, it will
decrease a plant’s hardiness to freezing temperatures. Most nitrogen
fertilizers are pure white in color. Most nitrogen fertilizers dissolve easily in
water and moves readily through the soil with irrigation water.
live, nitrogen represents the one nutrient that is universally in short supply.
Nitrogen helps to drive plant growth and causes increases in size. It
stimulates increased leaf and stem growth, causes a darkening of leaf color,
hastens plant growth after winter dormancy and helps to increase the amount of
food manufactured by the plant. If applied too late in the year, it will
decrease a plant’s hardiness to freezing temperatures. Most nitrogen
fertilizers are pure white in color. Most nitrogen fertilizers dissolve easily in
water and moves readily through the soil with irrigation water.
Slide 6. Lack of nitrogen shows up in plants as slow
growth, foliage with a light green color and a lack of density in the canopy.
growth, foliage with a light green color and a lack of density in the canopy.
Slide 7. In pine trees a lack of nitrogen shows up in the
same way. This translates to a canopy which is not full, small candles and
needles occupying the ends of branches while most of the branch is without
needles.
same way. This translates to a canopy which is not full, small candles and
needles occupying the ends of branches while most of the branch is without
needles.
Slide 8. If too much nitrogen is applied, plants might
grow rapidly with an extremely dense canopy and very dark color. When nitrogen
is applied in large amounts it can cause scorching to occur on leaves and tip
dieback on needles. In some cases it may cause plant death. Applying too much
nitrogen is a waste of money and causes environmental problems as well.
grow rapidly with an extremely dense canopy and very dark color. When nitrogen
is applied in large amounts it can cause scorching to occur on leaves and tip
dieback on needles. In some cases it may cause plant death. Applying too much
nitrogen is a waste of money and causes environmental problems as well.
Slide 9. Adequate amounts of phosphorus is most closely
related to good root growth and plant establishment, flowering and fruit
production, seed and oil production. When soils are cold and wet this can lead
to a lack of phosphorus taken up by plant roots. There is a quick recovery by
plants as soon as the soils begin to warm. Phosphorus fertilizers are typically
dark in color, usually dark gray or brown.
related to good root growth and plant establishment, flowering and fruit
production, seed and oil production. When soils are cold and wet this can lead
to a lack of phosphorus taken up by plant roots. There is a quick recovery by
plants as soon as the soils begin to warm. Phosphorus fertilizers are typically
dark in color, usually dark gray or brown.
Slide 10. Unlike nitrogen, phosphorus can stay present in
the soil for long periods of time, does not dissolve easily in water and does
not move through the soil unless the soil is very sandy. Phosphorus levels can
build in the soil with repeated applications of high levels. In some cases
phosphorus can build to toxic levels with repeated applications. Phosphorus can
interfere with other nutrients, iron in particular. Over application is a waste
of money and can lead to environmental pollution.
the soil for long periods of time, does not dissolve easily in water and does
not move through the soil unless the soil is very sandy. Phosphorus levels can
build in the soil with repeated applications of high levels. In some cases
phosphorus can build to toxic levels with repeated applications. Phosphorus can
interfere with other nutrients, iron in particular. Over application is a waste
of money and can lead to environmental pollution.
Slide 11. Deficiency of phosphorus can sometimes lead to
purple discoloration of the plant which disappears when phosphorus becomes
available again. This is very common to many plants in cold, wet soils.
purple discoloration of the plant which disappears when phosphorus becomes
available again. This is very common to many plants in cold, wet soils.
Slide 12. Potassium is sometimes underappreciated in
fertilizer applications. Deficiencies are hard to see since a deficient plant
gives no outward symptoms. Potassium chloride, a common potassium fertilizer
used in mixing fertilizers together, as a reddish-brown color.
fertilizer applications. Deficiencies are hard to see since a deficient plant
gives no outward symptoms. Potassium chloride, a common potassium fertilizer
used in mixing fertilizers together, as a reddish-brown color.
Slide 13. Over applying potassium usually will not harm
anything and it does not build up in the soil like phosphorus does. Deficiencies
of potassium can lead to a plant’s decreased tolerance to stresses such as
heat, cold, freezing, disease and others.
anything and it does not build up in the soil like phosphorus does. Deficiencies
of potassium can lead to a plant’s decreased tolerance to stresses such as
heat, cold, freezing, disease and others.
Slide 14. Nutrients
needed in smaller amounts. Of the seven nutrients needed in much smaller
amounts, iron, manganese and zinc are the ones most likely to be in short
supply for plants growing in alkaline soils. Of the three, iron is by far the
one found most efficient in plants. This is odd because iron is one of the most
abundant minerals on earth. The key to its limited availability to plants is
the pH or alkalinity of our soils.
needed in smaller amounts. Of the seven nutrients needed in much smaller
amounts, iron, manganese and zinc are the ones most likely to be in short
supply for plants growing in alkaline soils. Of the three, iron is by far the
one found most efficient in plants. This is odd because iron is one of the most
abundant minerals on earth. The key to its limited availability to plants is
the pH or alkalinity of our soils.
Slide 15. Desert
soils and available nutrients. This is a chart showing the availability of
plant nutrients as the pH of the soil changes from acid to alkaline. The pH
ranges at the bottom of the chart from 4.0 on the left to 10 on the far right.
The red rectangle on the chart represents the range of soil pH of our desert
soils. The bars running vertically across the graph represent each of the
nutrients. As this bar becomes thinner, that particular nutrient is less
available. Nutrients which decrease as the soil pH increases (becomes thinner
from left to right inside the red rectangle) include phosphorus, iron,
manganese, boron, copper and zinc. Of these nutrients, the ones more commonly
deficient to plants in our soils include iron, manganese and zinc. Iron is
found deficient in about 90% of the times a minor element is deficient in our
soils.
soils and available nutrients. This is a chart showing the availability of
plant nutrients as the pH of the soil changes from acid to alkaline. The pH
ranges at the bottom of the chart from 4.0 on the left to 10 on the far right.
The red rectangle on the chart represents the range of soil pH of our desert
soils. The bars running vertically across the graph represent each of the
nutrients. As this bar becomes thinner, that particular nutrient is less
available. Nutrients which decrease as the soil pH increases (becomes thinner
from left to right inside the red rectangle) include phosphorus, iron,
manganese, boron, copper and zinc. Of these nutrients, the ones more commonly
deficient to plants in our soils include iron, manganese and zinc. Iron is
found deficient in about 90% of the times a minor element is deficient in our
soils.
Slide 16. Another problem with our desert soils is the
lack of decaying organic material. Most productive soils contain anywhere from
3 to 5% organic matter. Our soils contain far less than 1/10 of 1% organic matter.
Decomposing organic matter helps to lower soil pH and adds nutrients to the
soil. As it is decomposing it improves the chemistry of our soils and its
physical structure. Organic matter helps to preserve soil moisture and
increases the amount of earthworms, soil fungi and bacteria and other
decomposing organisms. During the decomposition process, natural chelates are
released which help to improve plant health.
lack of decaying organic material. Most productive soils contain anywhere from
3 to 5% organic matter. Our soils contain far less than 1/10 of 1% organic matter.
Decomposing organic matter helps to lower soil pH and adds nutrients to the
soil. As it is decomposing it improves the chemistry of our soils and its
physical structure. Organic matter helps to preserve soil moisture and
increases the amount of earthworms, soil fungi and bacteria and other
decomposing organisms. During the decomposition process, natural chelates are
released which help to improve plant health.
Slide 17. Micronutrients.
The three micronutrients we are most concerned with when applying fertilizers
to our soils are iron, manganese and zinc.
The three micronutrients we are most concerned with when applying fertilizers
to our soils are iron, manganese and zinc.
Slide 18. When iron is not available to plants they
display very obvious outward symptoms. These symptoms include the yellowing of
new foliage, called chlorosis, while the veins of the leaves remain green if
the chlorosis is mild. In advanced stages of iron chlorosis or yellowing due to
a lack of iron, the leaves may turn entirely bright yellow without green veins.
display very obvious outward symptoms. These symptoms include the yellowing of
new foliage, called chlorosis, while the veins of the leaves remain green if
the chlorosis is mild. In advanced stages of iron chlorosis or yellowing due to
a lack of iron, the leaves may turn entirely bright yellow without green veins.
Slide 19. The use of rock mulches decreases soil organic
matter and the release of natural chelates in the soil. Plants intolerant of
these types of soils developed iron chlorosis in 4 to 5 years after they have
been planted.
matter and the release of natural chelates in the soil. Plants intolerant of
these types of soils developed iron chlorosis in 4 to 5 years after they have
been planted.
Slide 20. Plants with purple leaves such as purple leaf
plum developed leaves which are pink in color since their leaves are red to
begin with. If you look closely at the leaves, the veins are darker color but
they are dark red instead of dark green. Plants that have severe iron chlorosis
are intolerant of excessive heat and cold and the leaf margins typically scorch
when temperatures are high. Normally people relate the scorching of the edges
of the leaves as a lack of water and so they water more. Increased watering
frequency can lead to root death and increased leaf scorch and yellowing.
plum developed leaves which are pink in color since their leaves are red to
begin with. If you look closely at the leaves, the veins are darker color but
they are dark red instead of dark green. Plants that have severe iron chlorosis
are intolerant of excessive heat and cold and the leaf margins typically scorch
when temperatures are high. Normally people relate the scorching of the edges
of the leaves as a lack of water and so they water more. Increased watering
frequency can lead to root death and increased leaf scorch and yellowing.
Slide 21. Causes of iron chlorosis include high soil pH,
continuously wet soils, the use of rock mulches around plants which require
soils with higher organic matter, continuous applications of high phosphorus
fertilizers, mechanical damage to the roots or trunk from lying trimmers, mowers
or borers.
continuously wet soils, the use of rock mulches around plants which require
soils with higher organic matter, continuous applications of high phosphorus
fertilizers, mechanical damage to the roots or trunk from lying trimmers, mowers
or borers.
Slide 22. Iron
fertilizers and strategies. The typical strategies used to correct iron
deficiency include adding additional iron, lower the soil pH usually with the
addition of sulfur, applying soil chelates that help to keep iron available and
the addition of organic soil amendments which breakdown and improve the soil.
Iron fertilizers can be applied to the soil, sprayed on the foliage or injected
into the trunk or large limbs.
fertilizers and strategies. The typical strategies used to correct iron
deficiency include adding additional iron, lower the soil pH usually with the
addition of sulfur, applying soil chelates that help to keep iron available and
the addition of organic soil amendments which breakdown and improve the soil.
Iron fertilizers can be applied to the soil, sprayed on the foliage or injected
into the trunk or large limbs.
Slide 23. What is a
chelate? A chelate is a chemical which surrounds the nutrient and keeps it
available for plants to use. Without the use of chelates these nutrients are
changed into forms that the plant cannot use.
chelate? A chelate is a chemical which surrounds the nutrient and keeps it
available for plants to use. Without the use of chelates these nutrients are
changed into forms that the plant cannot use.
Slide 24. Desert
soils and the best chelates. There are many different kinds of chelates
used in agriculture. These include EDTA, DTPA, EDDHA and citrates. Some
chelates are better at keeping nutrients like iron available to plants than
others. The diagram on the right shows how different chelates begin to drop or
lose the iron as the pH of the soil increases with one exception. At the top of
the diagram you can note that the chelate known as EDDHA does not drop the iron
through the entire range of pH from 4 to 10. When the pH of the soil is not
known and you are applying iron chelate to the soil, it is best to select a
fertilizer with the iron chelated with EDDHA. Unfortunately, this is also the
most expensive of the iron chelates. If the soil pH is 7.5, the iron chelate
DTPA will be adequate and it is less expensive. Frequently iron chelates used in
fertilizers are iron EDTA which becomes ineffective when the pH exceeds 6.0.
When using iron chelates as a foliar spray it is very important to make sure
that the pH of the spray mix is appropriate for the chelate being used or
buffer the water to the appropriate pH or the iron will drop out of the
solution and not be effective.
soils and the best chelates. There are many different kinds of chelates
used in agriculture. These include EDTA, DTPA, EDDHA and citrates. Some
chelates are better at keeping nutrients like iron available to plants than
others. The diagram on the right shows how different chelates begin to drop or
lose the iron as the pH of the soil increases with one exception. At the top of
the diagram you can note that the chelate known as EDDHA does not drop the iron
through the entire range of pH from 4 to 10. When the pH of the soil is not
known and you are applying iron chelate to the soil, it is best to select a
fertilizer with the iron chelated with EDDHA. Unfortunately, this is also the
most expensive of the iron chelates. If the soil pH is 7.5, the iron chelate
DTPA will be adequate and it is less expensive. Frequently iron chelates used in
fertilizers are iron EDTA which becomes ineffective when the pH exceeds 6.0.
When using iron chelates as a foliar spray it is very important to make sure
that the pH of the spray mix is appropriate for the chelate being used or
buffer the water to the appropriate pH or the iron will drop out of the
solution and not be effective.
Slide 25. Manganese.
The visual symptoms of manganese deficiency can be confused with iron
deficiency. When either are deficient they both produce chlorotic or yellowing
leaves with green veins on new growth. About 90% of the time or more the
chlorosis will be due to iron, not manganese. A spray bottle containing an iron
or manganese chelate and buffered to the appropriate pH can be sprayed on the
foliage as a test. Response to a foliar applied chelate is rapid and you should
see results in less than 24 hours. And this will confirm which nutrient is in
short supply. Manganese chlorosis is treated the same way it is iron but using
a source of manganese instead. Manganese chelates are available as well as
manganese sulfate. Applications include soil applied, foliar sprays and
injection.
The visual symptoms of manganese deficiency can be confused with iron
deficiency. When either are deficient they both produce chlorotic or yellowing
leaves with green veins on new growth. About 90% of the time or more the
chlorosis will be due to iron, not manganese. A spray bottle containing an iron
or manganese chelate and buffered to the appropriate pH can be sprayed on the
foliage as a test. Response to a foliar applied chelate is rapid and you should
see results in less than 24 hours. And this will confirm which nutrient is in
short supply. Manganese chlorosis is treated the same way it is iron but using
a source of manganese instead. Manganese chelates are available as well as
manganese sulfate. Applications include soil applied, foliar sprays and
injection.
Slide 26. Zinc.
Zinc deficiency is relatively rare but when it does occur it results in what we
call “little leaf” and a rosette or cluster of leaves around the end of the
branch. Correction of zinc deficiency can be with zinc chelates or zinc sulfate
applied to the soil or to the foliage.
Zinc deficiency is relatively rare but when it does occur it results in what we
call “little leaf” and a rosette or cluster of leaves around the end of the
branch. Correction of zinc deficiency can be with zinc chelates or zinc sulfate
applied to the soil or to the foliage.
Slide 27. What is
the perfect fertilizer? The perfect fertilizer bills a reservoir of
nutrients in the soil or in plant tissue. It also replaces nutrients taken from
the soil and used by the tree. The perfect fertilizer maintains the plant in
good health so it is resistant to harsh environments and disease. Once you
become familiar with the soils of a geographic region and to begin having
success using certain fertilizers, soil tests become less important. But when
coming into a new area it is best to either perform some soil or foliar tests
or talk with your local farm or extension agent or NRCS representative.
the perfect fertilizer? The perfect fertilizer bills a reservoir of
nutrients in the soil or in plant tissue. It also replaces nutrients taken from
the soil and used by the tree. The perfect fertilizer maintains the plant in
good health so it is resistant to harsh environments and disease. Once you
become familiar with the soils of a geographic region and to begin having
success using certain fertilizers, soil tests become less important. But when
coming into a new area it is best to either perform some soil or foliar tests
or talk with your local farm or extension agent or NRCS representative.
Slide 28. Liebigs law of the minimum. The growth of
plants from the application of fertilizer is limited by the nutrient in the
least supply to the plant. If nitrogen is limiting the growth of trees, adding
phosphorus fertilizers will not stimulate growth. If phosphorus is limiting
growth, adding more nitrogen will not increase plant growth. One fertilizer or
nutrient cannot be substituted for a deficiency of another.
plants from the application of fertilizer is limited by the nutrient in the
least supply to the plant. If nitrogen is limiting the growth of trees, adding
phosphorus fertilizers will not stimulate growth. If phosphorus is limiting
growth, adding more nitrogen will not increase plant growth. One fertilizer or
nutrient cannot be substituted for a deficiency of another.
Slide 29. What is
the perfect ratio? The amount of nitrogen, phosphorus or potassium to apply
is dictated by the type of plant, previous fertilizers that were applied and
any soil tests that were done. Plants that are grown for their beauty such as
flowering trees may have a higher requirement for phosphorus than non-flowering
trees. In previous fertilizer applications, if fertilizers containing high
levels of phosphorus were used, phosphorus applications might be eliminated
entirely for a couple of seasons. Soil tests or foliar tests are the only
certain way of knowing what is lacking in the soil or in the plant. The problem
is that these can be expensive and adequate interpretation for landscape trees
and shrubs is lacking. Generally speaking fertilizers fruit trees and shrubs
should be high in nitrogen, moderately high to high and potassium but
phosphorus levels should be low. The same fertilizer ratios recommended for
turfgrass is is also adequate for nonflowering trees and shrubs. Flowering
trees and shrubs require higher amounts of phosphorus fertilizer.
the perfect ratio? The amount of nitrogen, phosphorus or potassium to apply
is dictated by the type of plant, previous fertilizers that were applied and
any soil tests that were done. Plants that are grown for their beauty such as
flowering trees may have a higher requirement for phosphorus than non-flowering
trees. In previous fertilizer applications, if fertilizers containing high
levels of phosphorus were used, phosphorus applications might be eliminated
entirely for a couple of seasons. Soil tests or foliar tests are the only
certain way of knowing what is lacking in the soil or in the plant. The problem
is that these can be expensive and adequate interpretation for landscape trees
and shrubs is lacking. Generally speaking fertilizers fruit trees and shrubs
should be high in nitrogen, moderately high to high and potassium but
phosphorus levels should be low. The same fertilizer ratios recommended for
turfgrass is is also adequate for nonflowering trees and shrubs. Flowering
trees and shrubs require higher amounts of phosphorus fertilizer.
Slide 30. What is
the perfect timing? General fertilizer applications to trees and shrubs is
normally done in late winter or early spring, preferably just before new growth
begins. Trees and shrubs that have a higher aesthetic value could be fertilized
with a split fertilizer application; half of the annual amount of fertilizer
applied in late winter and the other half just after flowering or fruiting. All
plants that are winter tender, subject to potential freeze damage, should not
receive any nitrogen fertilizer applications after August 1.
the perfect timing? General fertilizer applications to trees and shrubs is
normally done in late winter or early spring, preferably just before new growth
begins. Trees and shrubs that have a higher aesthetic value could be fertilized
with a split fertilizer application; half of the annual amount of fertilizer
applied in late winter and the other half just after flowering or fruiting. All
plants that are winter tender, subject to potential freeze damage, should not
receive any nitrogen fertilizer applications after August 1.
Slide 31. What is
the perfect amount? Adjust the rates of nitrogen application to the growth
observed in previous years. If good or excessive growth was observed, then
reduce your nitrogen application by half. If the plant has been in poor health
in previous seasons, increase the amount of fertilizer you might normally
apply. Generally, rates of application are equivalent to about 1 to 2 pounds of
nitrogen applied for every 1000 ft.² under the canopy of the tree. By using
ratios mentioned earlier, the proper amounts of phosphorus and potassium will
be applied. Foliar applications of fertilizer are applied after new growth has
begun but before hot weather. About 1 – 11/2 pounds of nitrogen is mixed in 100
gallons of spray solution and sprayed to run off. One foliar application is
typically not enough but three applications about two to three weeks apart
would be adequate. Iron chelates can be mixed in the spray solution and should
be applied multiple times if applied to the foliage. Correcting chlorotic
foliage with iron will require multiple applications about one week apart.
Foliar applications of fertilizers require wetting agents mixed in the spray
solution.
the perfect amount? Adjust the rates of nitrogen application to the growth
observed in previous years. If good or excessive growth was observed, then
reduce your nitrogen application by half. If the plant has been in poor health
in previous seasons, increase the amount of fertilizer you might normally
apply. Generally, rates of application are equivalent to about 1 to 2 pounds of
nitrogen applied for every 1000 ft.² under the canopy of the tree. By using
ratios mentioned earlier, the proper amounts of phosphorus and potassium will
be applied. Foliar applications of fertilizer are applied after new growth has
begun but before hot weather. About 1 – 11/2 pounds of nitrogen is mixed in 100
gallons of spray solution and sprayed to run off. One foliar application is
typically not enough but three applications about two to three weeks apart
would be adequate. Iron chelates can be mixed in the spray solution and should
be applied multiple times if applied to the foliage. Correcting chlorotic
foliage with iron will require multiple applications about one week apart.
Foliar applications of fertilizers require wetting agents mixed in the spray
solution.
Slide 32. How to
apply fertilizers. It is best to apply fertilizers in the same locations
where water is applied to the tree. If the tree is receiving water through drip
emitters, apply the fertilizer close to the drip emitters. Irrigations will
move the fertilizer into the rootzone. If the tree is growing in the lawn, the
fertilizer can be applied in concentric circles around the tree about 2 feet
apart. The fertilizer is placed 6 to 8 inches below the lawn to minimize uptake
of the fertilizer by the grass yet shallow enough so that the fertilizer is not
placed beneath the root system of the tree. Foliar applications of a fertilizer
require a wetting agent in the spray solution and multiple applications if this
is the only source of fertilizer. Foliar applied fertilizers are short-lived
and follow-up applications should be made 3 to 4 weeks apart.
apply fertilizers. It is best to apply fertilizers in the same locations
where water is applied to the tree. If the tree is receiving water through drip
emitters, apply the fertilizer close to the drip emitters. Irrigations will
move the fertilizer into the rootzone. If the tree is growing in the lawn, the
fertilizer can be applied in concentric circles around the tree about 2 feet
apart. The fertilizer is placed 6 to 8 inches below the lawn to minimize uptake
of the fertilizer by the grass yet shallow enough so that the fertilizer is not
placed beneath the root system of the tree. Foliar applications of a fertilizer
require a wetting agent in the spray solution and multiple applications if this
is the only source of fertilizer. Foliar applied fertilizers are short-lived
and follow-up applications should be made 3 to 4 weeks apart.
Slide 33. Late fall
fertilization. There is some evidence that late fall fertilization of trees
and shrubs can substitute for a late winter or early spring application. The
timing of this application is late enough in the season so that new growth is
not stimulated but well before leaf drop in the fall. Approximate dates might
be around mid-October.
fertilization. There is some evidence that late fall fertilization of trees
and shrubs can substitute for a late winter or early spring application. The
timing of this application is late enough in the season so that new growth is
not stimulated but well before leaf drop in the fall. Approximate dates might
be around mid-October.
Slide 34. Resources.